1. The Field of the Invention
The present invention relates to a circuit for protecting a laser indicator, more particularly, to a design of such a protective circuit which enables a laser light emitting diode (LED) to generate a stable laser light-spot while preventing the parts in the circuit from being damaged.
2. Description of the Related Art
In various situations such as a meeting, a symposium or a conference, etc., a speaker often uses an overhead projector, a projection screen and a plurality of overhead projector transparency sheets having an abstract and the summaries of the contents or graphics thereon to give a speech or report. If the projection screen is large, in order not to block a projecting light or to prevent the pictures on the projection screen to be uninteresting, the speaker uses a baton which is pointed to the corresponding texts and drawings on the projecting screen in conjunction with the contents of the speech or report.
Formerly, the baton which is most commonly seen is of a multisection telescopic structure which is pen-sized when contracted. When in use, the baton is extended and a front end of the extended baton is referred to as a guide. Such a structure cannot be used in a large-size projecting screen mostly due to a limitation in length and further the baton itself may block projecting light so that the projecting images will be interfered with.
On account of the development in electronics technology, among the new developing electronic products, a laser indicator substitutes for a conventional baton and solves these prior problems in use.
FIG. 2 shows an existing laser indicator 80 on the market. The configuration of the laser indicator 80 is like a pen on which a button 81 is installed. A laser light generated by a laser light emitting diode (LED) in the laser indicator 81 is focused to form a distinct red light-spot where the laser indicator 80 is pointed to and the related texts or drawings thereto are guided by the red light-spot.
The aforementioned laser indicator 80 has been increasingly popularized because of its compact size and ease of use together with an absence of shadow interference when in use.
Accordingly, the laser indicator 80 generates the laser light by using the laser LED and produces a laser light-spot on the screen at which the laser indicator 80 is pointed. Thus, the brightness and stability of the laser light-spot has a direct impact on an indicating performance of the aforesaid laser indicator 80. Therefore, how to make the laser LED in the laser indicator generate a stable laser light-spot is a main issue of the present invention.